Insufficient accuracy of trajectory measurements is a pressing problem for modern high-resolution airborne SAR systems. In the paper, a novel method for the estimation of residual trajectory deviations from SAR data is proposed. The method is based on the map-drift autofocus principle used to estimate the cross-track components of the aircraft acceleration on short time intervals. The estimated acceleration is then integrated to retrieve the residual trajectory deviations on the whole data frame. The proposed approach has been successfully tested with an X-band airborne SAR system.